1. Field of the Invention
The present invention relates to a polyolefin fiber and a method of producing the same. More particularly, the present invention pertains to a polyolefin fiber that includes a hydrophilic additive and titanium dioxide (TiO2), and optionally a spin finish on a surface thereof and is spun to have a circular section, a modified cross-section such as an X-shaped section, a Y-shaped section, a deltaic section, an oval section, a diamond section, a bladebone-shaped section, and a combined section thereof, or a combined section of the circular section and the modified cross-section, and a method of producing the same.
2. Description of the Related Art
Polypropylene (PP) that is light, has excellent wear resistance, and is produced by using a relatively simple process at low cost is used for various purposes such as plastics, films, fibers and the like.
Known polypropylene is very limited in use due to poor thermal and ultraviolet stabilities and a difficulty in dyeing. However, the development of catalysts improves a polypropylene polymerization process and the development of additives such as thermal stabilizers and UV stabilizers and pigments contributes to coloration. Accordingly, polypropylene is widely used for such as interior materials for vehicles and interior carpets.
The polypropylene fiber has advantages of low specific gravity, high resistance to chemicals, and low price as compared to other natural or synthetic fibers. Thus, the polypropylene fiber is applied to various types of non-woven fabric products. In particular, the low melting point (about 165° C.) of polypropylene is suitable for a thermal bond non-woven fabric process combining fiber webs by heat and it is commercially used. The thermal bond non-woven fabrics made of the polypropylene fiber are used as coverstocks of disposable sanitary goods such as diapers and sanitary napkins.
Furthermore, the polypropylene fiber may be subjected to needle punching to produce felts for vehicle trims, carpets, civil engineering drain materials, oil absorption fabrics, and filter substrates, or to various types of spinning processes to produce cotton yarns for cloths and filters.
Many studies have been made to develop a process for providing hydrophilicity to the polypropylene fiber along with a process for providing dyeability. However, in most studies, desirable processes were not obtained and it was difficult to produce fibers due to compatibility to polypropylene.
The polypropylene fiber that consists of only carbon and hydrogen atoms has very strong hydrophobicity, thus having limited use. Processes for providing hydrophilicity to hydrophobic polyolefin (for example, polyethylene, polypropylene or the like) fibers will be described below. JP-A-2-169774 discloses a method of attaching a hydrophilic surfactant such as polyester denatured silicon and sorbitan fatty acid ester to the surfaces of hydrophobic fibers. However, in the method, the initial hydrophilicity is excellent but it is maintained only over a short period of time, and the hydrophilic surfactant is removed by water during treatment of spunlaces, so that hydrophobicity of polypropylene is increased. WO 2000/0071789 discloses a method of melt mixing fatty acid monoglyceride that contains 80 wt % or more of glyceride and has 8 to 16 carbon atoms and hydrophobic fibers to produce polyolefin fibers. However, the method is disadvantageous in that fast surface migration of fatty acid monoglyceride reduces maintenance time of hydrophilicity and it is difficult to perform a master batch process and to perform mixing in respects to polyolefin resins due to liquid surfactants. JP-A-2-221448 discloses hydrophilic non-woven fabrics that are made of complex fibers containing 3 to 13 wt % of fatty acid monoglyceride having 12 or more carbon atoms and 3 to 15 wt % of polyvinyl alcohol or polyamide. However, in the complex fibers, fatty acid monoglyceride and polyvinyl alcohol or polyamide are contained in a very large amount. Accordingly, production cost thereof is high. Furthermore, since the fibers are applied to only complex spinning devices, the type of production devices is limited.
Meanwhile, the development of appropriate spin finishes and the advance of finishing technologies realize provision of hydrophilicity once or several times and improve the quality of coverstocks such as disposable diapers, sanitary napkins or the like. However, even though hydrophilicity is provided to the polypropylene fibers by spin finish treatment, the fibers are applied to only disposable goods, not semi-durable goods and durable goods having desirable maintenance of hydrophilicity due to poor maintenance of hydrophilicity. Furthermore, the fibers cannot be used for sanitary and industrial wipe goods that are produced by using a spunlace process. The reason is as follows. High pressure jet water is used as a medium during entanglement of webs, which removes the spin finishes applied on the fiber surface to get back to hydrophilicity, so that polypropylene has strong hydrophobicity.